During severe hyperinflation in Hungary during and after World War II, the Hungarian government created the 1 milliard B. pengo note. It was never issued, however. One milliard B. pengo corresponds to a denomination of . . .
1,000,000,000,000,000,000,000 pengo
To give you an idea of the magnitude of this number, if these were US dollars, it would be enough for every human on Earth to have over 200 billion dollars each!
The highest denomination issued was the next lower note which was 100,000,000 B. pengo note (only 20 billion dollars each :-).